The recent popularity of sports and leisure activities shows that more and more group activities, such as, hiking or bicycle-riding, are held. When people are involved in a group activity, a common problem is the fall behind of members of the group. A typical solution to the problem is to form a buddy system for mutual monitoring or confirm locations through the uses of radio walkie-talkie or mobile phones. As the kind of solution requires human intervene and lacks an automatic warning mechanism, accidents happen and urgent rescue operation is often delayed.
The existing fall behind warning technologies may be divided into three categories, as shown in FIG. 1. The first category is the manual fall behind warning technology, the second category is the semi-automatic fall behind warning technology and the third category is the automatic fall behind warning technology. In the first category, all the individuals of the group use either visual sighting or forming buddy system to monitor other members to prevent falling behind. In the second category, all the individuals of the group use wireless communication devices, such as walkie-talkie or mobile phone, to confirm the locations of one another to prevent falling behind. In the third category, all the individuals of the group use related positioning technology, such as global positioning system (GPS) or global system for mobile communication (GSM), to confirm the absolute location of one another to determine whether an individual is falling behind, and then use wireless communication technology, such as, RF or WiFi to automatically notify all the other individuals. The majority of the current technologies are in the second and the third categories.
The second category technologies, for example, include those disclosed by Ankang Le in IEEE “Sensor-based training optimization of a cyclist group” in 2007 and U.S. Pat. No. 6,832,153 “Method and Apparatus for Providing Pertaining to Vehicles Located Along a Predetermined Travel Route”. In the disclosed IEEE paper, a plurality of bicycles performs mutual communication to know one another's location to optimize the cyclist group training. When a member cyclist falls behind, the problem is verified through the mutual communication of the members. The disclosed U.S. patent uses a pre-determined travel route to perform group management. The vehicles obtain the GPS information during traveling and send the feedback information to the information center. If a vehicle does not travel along the pre-determined travel route, a warning is automatically sent out and reports to the information center.
The third category technologies for example, include those disclosed by Fatima Batool et al. in IEEE “An optimal route & vehicle assignment fleet management system with real-time monitoring” in 2005 and Jeremy Impson et' al. in IEEE “Portable wireless battlefield ministration tracking and information system” in 1999.
Fatima Batool et. al. use the optimal route to manage the vehicle fleet. A vehicle obtains the real-time GPS information during traveling. If the vehicle does not follow the pre-determined route, a warning is automatically sent to the remote management center to achieve the automatic fall behind warning. Jeremy Impson et. al. use a system with personnel equipped with GPS device to report the GPS location of the personnel to the administrative center in real time. The system is applicable to the battlefield for monitoring the personnel, emergency reporting and fall behind warning.
Third category technologies, for example, also include those disclosed by U.S. Pat. No. 6,504,503 and U.S. Pat. No. 6,216,391. U.S. Pat. No. 6,504,503 disclosed a peer-to-peer GPS using a communication device with embedded GPS. Through peer-to-peer wireless communication, the communication device with embedded GPS may communicate the location information with others to prevent falling behind. U.S. Pat. No. 6,216,391 disclosed a method for locating a GSM mobile station, with the absolute location information from trigonometry algorithm using GSM mobile phone and GSM mobile station. The absolute location of the communication device may be obtained through the method and then the location information is exchanged through wireless communication to prevent falling behind.
As the human intervene is required in both the first category and the second category technologies for repeated confirmation or lack of automatic warning mechanism, accidents happen and urgent rescue operation is often delayed. The third category technologies usually require expensive communication devices and additional environment deployment, such as, GPS satellite and wireless station. Also, as the high power wireless communication technology is used, the high power consumption is only suitable for short-term activity.